This application relates to a method of repairing a compressor or turbine blade airfoil, wherein super abrasive machining (SAM) quills are utilized to form the contour on the airfoil.
Gas turbine engines are known, and typically include a plurality of sections mounted in series. Two of the sections are the turbine section and the compressor section. These sections each include a plurality of rotors, each mounting a plurality of circumferentially spaced blades.
Air enters a gas turbine engine via a fan. Some air is bypass air, while some air enters a compressor section, where it is compressed. The compressed air moves downstream where it is mixed with fuel and is combusted in a combustor section. The hot products of combustion then move downstream over the turbine blades, driving them to rotate. The turbine blades exist in a very harsh environment, and may also be subject to rubbing with spaced stationary surfaces.
The turbine blades as known have very complex structures. As an example, complex cooling channels are formed within the blades, and receive cooling air to assist the blades in resisting high temperatures.
Even with the design of the cooling channels, etc., turbine blades will often wear. This is particularly true at the tip of an airfoil on the blade. Since the blades are formed with the complex channels, they are expensive. Thus, rather than simply replace worn blades, it has become standard in the industry to repair the blades.
The compressor blades are not subject to the high temperatures that the turbine blades face, but have their own challenges. As an example, sand or other impurities can damage the blade. Compressor blades are also repaired.
When either type blade has worn at the outer tip of its airfoil, one common technique for repairing the blade is to apply a weld material at the tip to return the blade to its original height. This weld material must then be machined such that it approximates the desired airfoil shape and height.
In the prior art, hand blending techniques, and grinding wheels are utilized. Also, milling may be used for restoring the tip and upper wall areas. Typically, hand blending is performed after a milling operation to meet finish requirements.
The prior art techniques are relatively time-consuming. Moreover, for smaller blades having an airfoil that curves around a smaller radius of curvature, the prior art grinding and machining tools may be too large.
Super abrasive machining techniques have been known and have been utilized for originally forming portions of turbine blades. As an example, U.S. Pat. No. 7,101,263 discloses a super abrasive machine tool. However, super abrasive machining techniques have not been utilized for repairing the tips of blade airfoils.